Biosynthesis of jasmonic Acid by several plant species

Six plant species metabolized ¹⁸O-labeled 12-oxo-cis,cis-10,15-phytodienoic acid (12-oxo-PDA) to short chain cyclic fatty acids. The plant species were corn (Zea mays L.), eggplant (Solanum melongena L.), flax (Linum usitatissimum L.), oat (Avena sativa L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.). Among the products was jasmonic acid, a natural plant constituent with growth-regulating properties. The pathway is the same as the one recently reported by us for jasmonic acid synthesis in Vicia faba L. pericarp. First, the ring double bond of 12-oxo-PDA is saturated; then β-oxidation enzymes remove six carbons from the carboxyl side chain of the ring. Substrate specificity studies indicated that neither the stereochemistry of the side chain at carbon 13 of 12-oxo-PDA nor the presence of the double bond at carbon 15 was crucial for either enzyme step. The presence of enzymes which convert 12-oxo-PDA to jasmonic acid in several plant species indicates that this may be a general metabolic pathway in plants.     

Similar stress responses are elicited by copper and ultraviolet radiation in the aquatic plant Lemna gibba: implication of reactive oxygen species as common signals

Metals and ultraviolet (UV) radiation are two environmental stressors that can cause damage to plants. These two types of stressors often impact simultaneously on plants and both are known to promote reactive oxygen species (ROS) production. However, little information is available on the potential parallel stress responses elicited by metals and UV radiation. Using the aquatic plant Lemna gibba, we found that copper and simulated solar radiation (SSR, a light source containing photosynthetically active radiation (PAR) and UV radiation) induced similar responses in the plants. Both copper and SSR caused ROS formation. The ROS levels were higher when copper was combined with SSR than when applied with PAR. Higher concentrations of copper plus PAR caused toxicity as monitored by diminished growth and chlorophyll content. This toxicity was more pronounced when copper was combined with SSR. Because the generation of ROS was also higher when copper was combined with SSR, we attributed this enhanced toxicity to elevated levels of ROS. In comparison to PAR-grown plants, SSR treated plants exhibited elevated levels of superoxide dismutase (SOD) and glutathione reductase (GR). These enzyme levels were further elevated under both PAR and SSR when copper was added at concentrations that generated ROS. Interestingly, copper treatment in the absence of SSR (i.e. copper plus PAR) induced synthesis of the same flavonoids as those observed in SSR without copper. Finally, addition of either dimethyl thiourea or GSH (two common ROS scavengers) lowered in vivo ROS production, alleviated toxicity and diminished induction of GR as well as accumulation of UV absorbing compounds. Thus, the potential of ROS being a common signal for acclimation to stress by both copper and UV can be considered.     

Systemic movement of Agrobacterium tumefaciens in several plant species

AIMS: The systemic movement of Agrobacterium spp. inside plants of different species was studied to determine the most valuable diagnostic methodology for their detection. METHODS AND RESULTS: Pathogenic agrobacteria were detected by isolation and PCR in tissue away from primary tumours in tomato plants grown in the presence of Agrobacterium spp. Moreover, this bacterium was also able to induce secondary tumours beyond the inoculation site. In addition, the capacity of agrobacteria to translocate and induce secondary tumours was analysed in rose, grapevine, chrysanthemum, cherry and peach x almond hybrid GF677. No differences among strains of Agrobacterium spp. were detected in secondary tumour development, although some of them induced a significantly higher number of primary tumours in some species. Movement of inoculated pathogenic cells of four strains was also demonstrated in symptomless portions of the plant stems by isolation and PCR. Finally, pathogenic agrobacteria were detected in root, crown and stem portions of naturally infected walnuts. In all assays, PCR was the most efficient technique for detecting the movement of Agrobacterium spp. within the plants. CONCLUSIONS: Migration of agrobacteria inside plants is a complex phenomenon and more extensive than previously reported. Therefore, efficient and sensitive detection methods such as PCR must be used to select clean plants to avoid latent infections of Agrobacterium spp. SIGNIFICANCE AND IMPACT OF THE STUDY: The results show that migration of Agrobacterium spp. could be relatively frequent in several cultivated fruit trees, and systemic infections should be taken into account when designing strategies for controlling crown gall disease.     

Nitrogen mineralization in heathland ecosystems dominated by different plant species

Net N mineralization rates were measured in heathlands still dominated by ericaceous dwarf shrubs (Calluna vulgaris or Erica tetralix) and in heathlands that have become dominated by grasses (Molinia caerulea or Deschampsia flexuosa). Net N mineralization was measuredin situ by sequential soil incubations during the year. In the wet area (gravimetric soil moisture content 74–130%), the net N mineralization rates were 4.4 g N m^–2 yr^–1 in the Erica soil and 7.8 g N m^–2 yr^–1 in the Molinia soil. The net nitrification rate was negligibly slow in either soil. In the dry area (gravimetric soil moisture content 7–38%), net N mineralization rates were 6.2 g N M-2 yr^–1 in the Calluna soil, 10.9 g N m^–2 yr^–1 in the Molinia soil and 12.6 g N m^–2 yr^–1 in the Deschampsia soil. The Calluna soil was consistently drier throughout the year, which may partly explain its slower mineralization rate. Net nitrification was 0.3 g N m^–2 yr^–1 in the Calluna soil, 3.6 g N m^–2 yr^–1 in the Molinia soil and 5.4 g N m^–2 yr^–1 in the Deschampsia soil. The net nitrification rate increased proportionally with the net N mineralization rate suggesting ammonium availability may control nitrification rates in these soils. In the dry area, the faster net N mineralization rates in sites dominated by grasses than in the site dominated by Calluna may be explained by the greater amounts of organic N in the soil of sites dominated by grasses. In both areas, however, the net amount of N mineralized per gram total soil N was greater in sites dominated by Molinia or Deschampsia than in sites dominated by Calluna or Erica. This suggests that in heathlands invaded by grasses the quality of the soil organic matter may be increased resulting in more rapid rates of soil N cycling.     

Optical parameters of leaves of 30 plant species

Optical parameters (absorption coefficient k, infinite reflectance R∞, scattering coefficient 8) are tabulated for seven wavelengths and analyzed for statistical differences for 30 plant species. The wavelengths are: 550 nm (green reflectance peak), 650 nm (chlorophyll absorption band), 850 nm (infrared reflectance plateau), 1450 nm (water absorption band), 1650 nm (reflectance peak following water absorption band at 1450 nm), 1950 nm (water absorption band), and 2200 nm (reflectance peak following water absorption band at 1950 nm).     

Phytoremediation of anthracene contaminated soils by different plant species

Phytoremediation is perceived as an alternative technology for contaminated site remediation. Yet, the mechanisms plants use to remove organic contaminants have not been fully elucidated. The objective of the current study was, therefore, undertaken to clarify the contribution of plants to the disappearance of organic contaminants in soil. Four plant species, including alfalfa, tall fescue, barley, and orchard grass, were examined for the ability to facilitate the degradation of the polyhydric aromatic hydrocarbon, anthracene. Soil samples were intermittently collected for two months to measure the disappearance of anthracene and bacterial number by GC and epifluorescence microscopy, respectively. Plant exudates were collected to determine their ability to solubilize anthracene. Alfalfa showed a 28% enhancement in the disappearance of anthracene compared to the unplanted control. Root exudates from alfalfa increased the release of soluble anthracene by 25 to 80% compared to the other species and unplanted controls. Among the plants tested, there was a positive correlation between enhancing the disappearance of anthracene by plants grown in soil and increasing the release of anthracene by isolated plant exudates. The results suggest that root exudates facilitate the mobilization of anthracene from soil and that the successful implementation of phytoremediation depends on the plant species. Further, root exudates may be a useful tool in screening plants for possible application in anthracene remediation.     

Synthesis of distinctly different sets of antimicrobial activities by elicited plant cell suspension cultures

The aim of this study was to evaluate the potential of plant suspension cultures for the production of antimicrobial activities. The extracellular, intracellular and cell wall bound fractions of 16 heterotrophic, photoautotrophic and photomixotrophic plant cell suspension cultures each treated with nine different elicitors were tested for the elicitor dependent production of antimicrobial activities. Distinctly different patterns of bioactivities directed against a panel of human isolates including Gram-positive (Bacillus subtilis, Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria as well as fungi (Candida maltosa) were identified for all except the two autotrophic cell cultures. The intracellular fractions of elicited cell cultures were more active than extracellular fractions while cell wall bound fractions showed almost no activities. The intracellular fraction of heterotrophic Lavendula angustifolia cells elicited with a preparation of Pseudomonas syringae was the most active fraction against Candida maltosa. The intracellular fraction of photomixotrophic Arabidopsis thaliana cells elicited with salicylic acid was active against all test isolates. An antimicrobial protein could be identified and partially purified from this culture. Our findings suggest that elicited plant cell cultures may present a new promising alternative source of antimicrobial proteins.     

Host plant specificity in several species of generalist mite predators

1. Species in the genus Neoseiulus are considered to be generalist predators, with some species used in biological control programmes against phytophagous mites and insects. 2. A general survey of Neoseiulus species in inland Australia indicated that different species are associated with particular tree species. This pattern of host plant use was investigated for four Neoseiulus species (N. buxeus, N. cappari, N. brigarinus, N. eremitus) by means of a sampling programme through time and across space. 3. Each species of Neoseiulus was collected entirely or mostly from one species of tree; little or no overlap was detected despite the tree species growing in well‐mixed stands. Host plant specificity thus appears to be strong in this genus. 4. Species in two other genera (Pholaseius and Australiseiulus), also considered to be predatory, showed a similar association with particular tree species. 5. The implications for the use of these predators in biological control are considerable. In particular, phytoseiid species with specific needs in terms of host plants may not be suitable for use as general purpose predators. Meeting the needs of phytoseiids through the modification of host plant attributes may be a step towards enhancing their efficacy as biological control agents.     

Protoplast culture and plant regeneration of several species in the genus Dianthus

Summary Seventeen cultivars belonging to the genus Dianthus were examined for protoplast isolation, culture and shoot regeneration under the same conditions. These included D. caryophyllus, D. chinensis, D. barbatus, D. plumarius, D. superbus and D. japonicus as well as interspecific hybrid cultivars (D. caryophyllus x D. chinensis and D. chinensis x D. barbatus). In all cultivars, viable protoplasts were isolated at high yields from leaves of axenic shoot cultures and some of these protoplasts divided and formed colonies. However, shoot regeneration frequencies were markedly different among the species. High frequency shoot regeneration was obtained from D. chinensis and interspecific hybrid cultivars, while only low frequency or no shoot regeneration was obtained from other species.Abbreviations MS Murashige and Skoog (1962) - FW fresh weight - MES 2-N-morpholinoethane sulfonic acid - FDA fluoroscein diacetate - NAA 1-naphthaleneacetic acid     

Biochemical signals and biological responses elicited by the focal adhesion kinase

The focal adhesion kinase, FAK, is an important component of an integrin-dependent signaling pathway, which functions to transmit signals from the extracellular matrix into the cytoplasm. FAK is an essential gene product, since the fak-/- mouse exhibits embryonic lethality. A number of important biological processes, including cell motility and cell survival, are controlled by integrin-dependent signals and FAK has been implicated in regulating these processes. This review will focus upon recent findings providing insight into the mechanisms by which FAK transmits biochemical signals and elicits biological effects.     

The characterization of phenylalanine ammonia-lyase from several plant species

Inhibition of the enzyme phenylalanine ammonia-lyase is considered as a target for the design of herbicides. A reliable and simple assay for the enzyme has been used and the kinetics of the enzyme from several sources compared. Purification of the enzyme from the grass green foxtail (Setaria glauca) did not change its kinetic behavior. The distribution of phenylalanine ammonia-lyase and tyrosine ammonia-lyase activity in various plant species was determined.     

The effect of atmospheric humidity on photosynthesis,transpiration and water use efficiency of leaves of several plant species

The effect of humidity on the gas exchange of leaves of the dicotyledons soybean (Glycine max (L.) Merrill), sunflower (Helianthus annuus L.), jojoba (Simmondsia chinensis (L.) Schneider), and saltbush (Atriplex halimus L.) and the monocotyledons wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) sorghum (Sorghum bicolor (L.) Moench) and barnyard grass (Echinochloa crus-galli (L.) Beauv.) was examined under conditions of adequate soil moisture in a controlled environment. Photosynthesis and stomatal and internal diffusion resistances of whole, attached, single leaves were not affected by changes in humidity as the vapour pressure deficit between the leaf and atmosphere ranged from 8 to 27 mb. Transpiration increased linearly with increasing vapour pressure deficit. Whole plants of barley exhibited a different response. As humidity was increased, photosynthesis increased, transpiration expressed per unit of vapour pressure difference increased, and diffusion resistances became smaller. Reasons for the different behaviour of single leaves and whole plants are suggested. An index for water use efficiency, expressed per millibar of vapour pressure deficit, was calculated for single leaves of each species used in the experiments. This showed that water use efficiency was highest in the C₄ xerophytes and lowest in the C₃ mesophytes. The effect of environment on water use efficiency is examined using data from the literature.     

Metabolic pathways and synthetic ability of leaves of several pyrus species

Relationship between type of metabolism and synthetic ability of leaves of several pear species was investigated. Species incorporating high quantities of labelled glucose into the alcohol insoluble fraction of the leaf respired through the Embden-Meyerhof-Parnas glycolitic pathway and citric-acid-cycle sequence. Species incorporating small amounts of glucose respired mostly through the pentose phosphate pathway. As leaves aged, their synthetic ability decreased, and respiration changed toward the pentose phosphate pathway. When species (having leaves of the same age) were compared, respiration through the pentose phosphate pathway seemed to be associated with small leaf size. It was concluded that the type of respiration in leaves was determined by the energy requirement for synthetic processes. When the energy requirement was low, metabolism of leaves proceeded through the pentose pathway. The synthetic ability in turn was influenced genetically, by environment, or by the age of the leaf.     

Utilization of phosphate from different sources by six plant species

Summary Six plant species, wheat, paspalum grass (Paspalum plicatulum), maize, molasses grass (Melinis minutiflora), soybean and buckwheat (Fagopyrum esculentum) were compared for their abilities to utilize phosphate from superphosphate, a calcined aluminum phosphate and four rock phosphates.Buckwheat showed an exceptional behaviour in that it could utilize all phosphates. For the other plants, only the calcined aluminum phosphate and one rock phosphate (hyperphosphate) had significant fertilizing values. Their efficiencies, relative to superphosphate, were 0.45 and 0.11 for wheat, 0.73 and 0.43 for paspalum grass, 0.50 and 0.37 for maize, 0.46 and 0.42 for molasses grass, 0.28 and 0.38 for soybean, and 0.72 and 1.08 for buckwheat, respectively.For three P sources, superphosphate, calcined aluminum phosphate and hyperphosphate, a relationship between soil acidity and P uptake was found. Soil pH in its turn was negatively related to the ratio of total equivalents of cations and those of anions absorbed. Consequenly, P uptake was positively related to the ratio of total equivalents of cations to those of anions absorbed. The same effect of plant species on soil pH could also explain the difference in uptake of P from sparingly soluble phosphates. The relative efficiencies of calcined aluminum phosphate and hyperphosphate for the various plant species were closely related to the ratio of total cations and total anions absorbed by these plants.on leave at the Agricultural University during 1977.     

Four new yeast species of the genus Sporobolomyces from plant leaves

Among the ballistoconidium-forming yeast strains isolated from various plant leaves collected in North and Northeast China, 12 strains forming orange to orange-red colored colonies were revealed to represent four novel species of the genus Sporobolomyces by conventional, chemotaxonomic and molecular phylogenetic studies, based on the 26S-rDNA D1/D2 domain and internal transcribed spacer (ITS) region sequences. Sporobolomyces beijingensis sp. nov., represented by eight strains (type strain CB 80T = AS 2.2365T = CBS 9730T), and Sporobolomyces jilinensis sp. nov., represented by two strains (type strain CB 118T = AS 2.2301T = CBS 9728T), clustered in the Johnsonii clade of the Sporidiobolus lineage. Sporobolomyces clavatus sp. nov., represented by strain CB 281T (= AS 2.2318T = CBS 9729T), belonged to the Agaricostilbum lineage and showed a close relationship to Sporobolomyces ruber and Sporobolomyces dracophylli. Sporobolomyces symmetricus sp. nov., represented by strain CB 64T(= AS 2.2299T = CBS 9727T), formed nearly symmetrical ballistoconidia and was closely related with Sporobolomyces vermiculatus and Sporobolomyces gracilis in the Gracilis clade of the Erythrobasidium lineage.     

Presence of single-chain ribosome-inactivating protein-like activities in several plant species.

The present screening work was devoted to the search for new ribosome-inactivating proteins (RIPs) in 21 plant species. Eight plants proved to be very active, inhibiting protein synthesis in eukaryotic in vitro systems (rat liver, Vicia sativa and wheat germ). They fulfil the major requirements for consideration as type 1 RIPs. Also, eight plants were found to contain haemagglutinating activity of human red cells but this was not related to the simultaneous presence of RIPs.     

Uptake system of silicon in different plant species

The accumulation of silicon (Si) in the shoots varies considerably among plant species, but the mechanism responsible for this variation is poorly understood. The uptake system of Si was investigated in terms of the radial transport from the external solution to the root cortical cells and the release of Si from the cortical cells to the xylem in rice, cucumber, and tomato, which differ greatly in shoot Si concentration. Symplasmic solutions of the root tips were extracted by centrifugation. The concentrations of Si in the root-cell symplast in all species were higher than that in the external solution, although the concentration in rice was 3- and 5-fold higher than that in cucumber and tomato, respectively. A kinetic study showed that the radial transport of Si was mediated by a transporter with a K(m) value of 0.15 mM in all species, but with different V(max) values in the order of rice>cucumber>tomato. In the presence of the metabolic inhibitor 2,4-dinitrophenol, and at low temperature, the Si concentration in the root-cell symplast decreased to a level similar to that of the apoplasmic solution. These results suggest that both transporter-mediated transport and passive diffusion of Si are involved in the radial transport of Si and that the transporter-mediated transport is an energy-dependent process. The Si concentration of xylem sap in rice was 20- and 100-fold higher than that in cucumber and tomato, respectively. In contrast to rice, the Si concentration in the xylem sap was lower than that in the external solution in cucumber and tomato. A kinetic study showed that xylem loading of Si was also mediated by a kind of transporter in rice, but by passive diffusion in cucumber and tomato. These results indicate that a higher density of transporter for radial transport and the presence of a transporter for xylem loading are responsible for the high Si accumulation in rice.     

Effect of ageing in the early biochemical signals elicited by PTH in intestinal cells

In previous work, we have demonstrated that rPTH(1-34) increases cytoplasmic calcium concentration ([Ca(2+)](i)) in isolated rat enterocytes. In the present study, we have identified the sources of PTH-mediated increase in [Ca(2+)](I) and the implication of Ca(2+) on hormone early signals in enterocytes isolated from young (3-month-old) and aged (24-month-old) rats. In young enterocytes, PTH raised [Ca(2+)](i) in a dose-dependent manner (1 pM-100 nM). In cells from aged rats, hormone concentrations higher than physiological (>/=1 nM) were required to observe significant increases in [Ca(2+)](i). Phospholipase C (PLC) inhibitors blocked the initial acute elevation of the [Ca(2+)](i) biphasic response to PTH of young enterocytes while in old cells, no effects were observed. The voltage-dependent calcium-channel blocker (VDCC), nitrendipine, suppressed PTH-dependent changes of the sustained [Ca(2+)](i) phase in young and aged animals. In this study, we analysed, for the first time, alterations in phosphatidylinositol 3-kinase (PI3K) activity and response to PTH in rat enterocytes with ageing. Basal PI3K activity was significantly modified by ageing. Acute treatment with 10(-8) M PTH increased enzyme activity, with a maximun at 2 min (+3-fold) in young rats and only elevated by less than 1-fold basal PI3K activity in aged animals. Hormone-induced tyrosine phosphorylation of p85alpha, the regulatory subunit of PI3K, as well as the phosphorylation on Thr(308) of its downstream effector Akt/PKB was evident in enterocytes from 3-month-old rats, whereas it was greatly reduced in the cells from 24-month-old animals. Intracellular Ca(2+) chelation (BAPTA-AM, 5 microM) affected the tyrosine phosphorylation of p85alpha and inhibited PTH-dependent PI3K activation by 75% in young rats and completely abolished the enzyme activity in aged animals, demonstrating that Ca(2+) is required for full activation of PI3K in enterocytes stimulated with PTH. The Thr phosphorylation of PI3K downeffector, Akt/PKB, was also fully dependent on Ca(2+). Taken together, these results suggest that PTH regulation of enterocyte [Ca(2+)](i) involves Ca(2+) mobilization from IP(3)-sensitive stores and the influx of the cation from the extracellular milieu, the former pathway being blunted during ageing. The data also indicates a positive role for intracellular calcium in one of the early signals of PTH in rat enterocytes, the activation of PI3K, and that hormone regulation of PI3K activity and Akt/PKB phosphorylation on Thr(308) is impaired with ageing.     

Distribution of lipoxygenase and hydroperoxide lyase in the leaves of various plant species

The enzyme activity responsible for volatile C₆-aldehyde formation was accompanied by lipoxygenase and hydroperoxide lyase in the green leaves of 28 plant species tested, but the level of each enzyme's activity varied. Lipoxygenase activity rather than hydroperoxide lyase activity appears to affect the overall C₆-aldehyde formation. There was a positive correlation (r = 0.712) between hydroperoxide lyase activity and the chlorophyll content of the green leaves; no correlation was found between lipoxygenase activity and chlorophyll content.